In general, electronic devices such as a liquid crystal display device and a semiconductor device are manufactured by forming patterns of multiple layers on a substrate. In order to form these patterns, a photolithography process has been usually used up to now. However, the photolithography process has problems in that the manufacturing process is complicated, and a large amount of chemical wastes harmful to the environment are generated because predetermined pattern masks need to be manufactured and chemical etching and stripping processes need to be repeated. This leads to an increase in manufacturing costs, thereby degrading competitiveness of products. A roll printing method using a printing roll has been proposed as a new method of forming patterns in order to solve the disadvantages of the photolithography process.
There are various roll printing methods, but the methods may be largely classified into two methods of a gravure printing method and a reverse offset printing method.
The gravure printing is a printing method that performs printing by covering ink on a concave plate and scratching extra ink and has been known as a method suitable for printing of various fields such as publication, packaging, cellophane, vinyl, and polyethylene, and studies for applying the gravure printing method to manufacturing active devices or circuit patterns applied to display devices have been conducted. Since the gravure printing transfers ink to a substrate by using a transfer roll, the patterns may be formed by a one-time transfer by using a transfer roll corresponding to an area of a desired display device even in the case of a large-area display device. The gravure printing may form the ink patterns for resist on the substrate and may be used to pattern various patterns of display devices, for example, not only a TFT, but also a gate line and a data line which are connected to the TFT, a pixel electrode, and a metal pattern for a capacitor, in the case of a liquid crystal display device.
However, a blanket typically used for gravure printing is manufactured by casting a silicone-based resin into a solid master mold, and the blanket thus manufactured has a limitation in being manufactured so as to have a uniform thickness and is also difficult to be mass-produced on a pilot scale. Thus, in order to form precisely fine patterns, the reverse offset printing method is usually adopted.
For the related art relating to the reverse offset printing method and the printing apparatus, it is possible to refer to the following Documents 1 to 4 which were filed and published by an applicant of the present invention.
The entire contents of the specifications of the following Documents 1 to 4 are a description of the related art of the present invention and are hereby incorporated by reference into the specification of the present invention.